1. Field of the Invention
This invention relates to a method of efficiently removing chromium ions from an aqueous solution of an organic acid containing chromium.
2. Description of the Prior Art
An aqueous solution of an organic acid is often handled industrially by using an apparatus made of stainless steel.
The recovery of such organic acids from an aqueous solution containing them has been carried out by extraction and distillation operations. When the acid is in aqueous solution it has been known to produce tert-butyl alcohol by reacting the water with isobutylene and separating the acid. These methods are mentioned in Japanese patent application Nos. 32116 and 126603/1975.
In these cases, however, depending on the operating conditions, such metals as iron, nickel and chromium may dissolve in the liquid mixtures, due to the corrosion of the stainless steel material, thus contaminating the final products. It is often required to remove such contaminating metals, usually for the prevention of the poisoning and toxicity of catalysts or for other related reasons. For example, in the methods mentioned in the above described Japanese published patent application Nos. 32116 and 126603/1975, the metallic ions in a circulating aqueous solution of an organic acid are removed. When such removal of metallic ions is necessary, a usual method would be to remove the metals by ion exchange chromatography using a cation exchange resin. When the present inventors attempted to remove such metallic ions by standard ion exchange methods they unexpectedly encountered the problem that while iron and nickel may be removed chromium is hardly removed, if at all.
As a result of continuing investigation of this problem, the present inventors have discovered an improved process for solving the separation problems of prior art methods.